1. Field of the Invention
The invention relates to calorimeters, and more particularly, relates to the ignition of a sample within a calorimeter.
2. Related Art
A sample material which is to be tested in a calorimeter is normally ignited using one of two methods.
In the first instance use is made of a length of resistance or fuse wire which is positioned so that it contacts a sample material which is in a calorimeter and which is to be ignited. An electric current is passed through the wire which is thereby heated to a temperature which causes ignition of the sample material. Although this technique works satisfactorily the resistance wire has a short life time and, in some applications, must be replaced after the combustion of each sample material.
It is also known to make use of a combustible thread such as cotton which is brought into contact with, or positioned so that it extends into, the sample material. A portion of the thread is attached to a resistance or fuse wire which is heated by passing an electrical current through the wire. When the temperature of the wire is increased sufficiently the thread is ignited and burns along its length and the flame ignites the sample material once the flame reaches the sample material. Again this process works satisfactorily but it suffers from the drawback that a correctly positioned fresh thread must be inserted into the calorimeter each time a sample is to be ignited.
Many calorimeters have been automated so that practically all the required steps in a calorimetric measurement are automatically carried out in the correct sequence. The problem associated with igniting the sample material, ie. the repeated replacement of the resistance wire or combustible thread, as the case may be, has however mitigated against the implementation of a completely automated process.